.gitignore: ignore terraform files

In anticipation of adding some terraform config, ignore some
terraform files.

Change-Id: Ic616c58d9b2b983852678aa072cbeb771b143887
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/369834
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..95708bc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+**/.terraform/*
+.terraform.lock.hcl